The front portion of the eye, and particularly the human eye, comprises a lens, an iris determining the effective diameter of the lens, and a cornea covering the iris and lens. The adult lens is normally clear and includes a relatively hard nucleus surrounded by a relatively soft cortex. Some lenses ultimately become partially or totally opaque, the opacity being known as a cataract.
The treatment of a cataract presently involves removal of the cataract from the eye by surgical means. There are presently three different techniques used for cataract surgery. The first is called intracapsular cataract surgery. In this method, an incision from 12-15 mm is made into the eye and the entire lens, including capsule, cortex and nucleus is removed en bloc. The second is called extracapsular cataract surgery. In this method an incision of 10-12 mm is made and the lens removed in pieces leaving the posterior capsule inside the eye. This method has been gaining in popularity because it makes use of the posterior capsule to support an intraocular lens. The third is called phakoemulsification. In this method, a 3 mm incision is made and the lens removed in pieces. The relatively large hard nucleus (8-11 mm in diameter) is removed through a 3 mm incision by use of an ultrasonic vibrating tip that is inserted inside the eye. When this tip is brought in contact with the hard nucleus the nucleus is shattered by direct contact with the rapidly vibrating tip. The method can be associated with high complication as the ultrasonic tip can permanently damage portions of the eye, such as the cornea when such a portion is contacted.